Sound system



Nov 27, 1962 I R. RANGER 3,066,189

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Nov. 27, 1962 R. H. RANGER 3,

SOUND SYSTEM Filed May 2, 1960 5 Sheets-Sheet 3 RICHARD H. RANGER INVENTOR.

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Nov. 27, 1962 R. H. RANGER 3,066,139

SOUND SYSTEM F'iled May 2, 1960 5 Sheets-Sheet 5 RICHARD H RANGER INVENTOR.

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3,066,189 SOUND SYSTEM Richard H. Ranger, Newark, Ni, assignor to Laura Lewis Ranger, executrix of said Richard H. Ranger,

deceased, assignor to Rangcrtone Electronics Corp Newark, N.J., a corporation of New Jersey Filed May 2, 1960, Ser. No. 26,092 1 Claim. (Cl. 179-1) This invention relates to a sound propagation system, and more particularly to a sound system for the improvement of the sound reproduction from the stage in a theatre, auditorium, hall, or the like.

Rapport between actors and audience is that element which gives the legitimate theatre its outstanding entertainment feature. It is that interchange across the footlights that makes the vibrant experience with the audionce as much a 'part of the show as the actors, and sight and sound are, of course, the main media for this interchange. The system of my invention functions to strenghten the actors or speakers voices by amplification, without the audience being conscious of the fact that the sound from the performers is being amplified.

There has been a tendency not to use amplification in the legitimate theatre because of its possible artificiality. It is expected that the actors themselves should be capable of projecting their voices anywhere in the theatre. With the economics of the situation as they are, however, large halls are necessary for adequate seating facilities to meet the overhead of even the best productions, and experience shows that actors are often unable to reach all the members of the audience in such large halls. Further, strained voices do not promote quality.

In order to put the sound across in large theatres, sound amplification systems have been used. The chief objection to theatre amplification systems has been the fact that the reinforced sound from the loudspeakers can take a dominating position over'the direct voice of the actor. This is due, primarily, to the fact that the sound from the loudspeakers reaches the audience ahead of the direct sound from the actors, which, in turn, is due atent C to the positioning of the loudspeakers closer to the lis- I teners than the distance from the actor to the listener. Since electrical energy passes from the microphcnes to the loudspeakers more quickly than the sound energy through the air, the direct sound from the stage arrives after the amplified sound from the loudspeakers. Under natural conditions without amplification the sound reaching a listeners cars is a composite comprising the direct sound from the speaker and reflected sound from walls, floors and objects, such as furniture, and the like. Furthermore, this reflected sound comes at different angles from the source, and is not a replica of the direct sound. Our two cars unconsciously pick up these variations as all parts of the original whole and come up with a composite integration which carries more information than the direct sound above does. Usually, the first sound to reach the listener in such a composite sound is the direct sound and, therefore, a listener reasons intuitively that the first sound to reach him establishes the direction of the source. Hence, in prior art arrangements wherein the loudspeakers are positioned closer to the listener than the actor, the sound has an auditory effect that is unnatural. If the loudspeakers are inartistically dis tributed throughout the hall, or theatre, an auditory effect which is jumpy is produced, one that seems to be composed of separate sounds coming from difierent parts 3,066,189 Patented Nov. 27, 1962,

of the theatre. If the system employs a plurality of loudspeakers which are concentrated in location, the sound appears to originate therefrom, and if this amplifled sound is identical and comes out of separated speak ers the total effect is most disturbing and unreal. However, it is possible to overcome this precedence effect of the electrically amplified sound and thus give it reality in the composite sound. For this purpose, magnetic recording has heretofore been tried in various forms where the time the recording medium takes to pass from the recording head to the playback head is used to bring the electrical amplification down to the natural time it takes the stage voices to reach the listener. This time delay is inserted in the amplification to the loudspeaker so that the direct voice will take precedence. This, however, has not become a popular method becauses it involves rotating equipment and rather continuing maintenance.

As another means of improving the sound from a stage, stereophonic reproduction of the voice has been proposed as given, for example, in the article by Dr; L. L. Beranek in the Journal of the Acoustical Society of America, vol. 26, p. 674, September 1954. This ar rangement includes a first group of microphones in the footlight area of a stage followed by a second series across the stage and finally by the microphones at the rear of the stage. Three channels are employed in the illustrated amplification system, comprising basically Left, Center and Right channels; The microphones are allocated in the usual stereophonic manner from left to right progressively, so that the microphones on the left of the Stage carry to the left speaker channel, the center microphones to the center speaker channel and the right microphones to the right speaker channel. The sound is supposed to come out of the loudspeakers cor respondingly in these channels. As is pointed cutin the article, however, there is a great tendency for such system to feedback when such a large group of micro phones are kept open. The sound control operator, therefore, has to be quite adroit in bringing up only those microphones located adjacent the actors who are speaking. Furthermore, the effective addition of sever interpretations of the same voice are lost.-

The sound system of my invention avoids the shortcomings of prior art arrangements by positioning, when possible, the loudspeakers no closer to the audience than are the actors themselves. Further, my novel system includes a plurality of communication channels (a minimumof two channels-and preferably three) with each channel comprising at least one loudspeaker and a'pair of microphones, with one microphone of each pair thereof being located at opposite sides of the stage. The microphones are spaced along the front of the stage such that the actors voice substantially always reaches at least one microphone of each communication channel whereby his voice is carried independently to each channel loudspeaker. Further, the channel loudspeakers are prefer ably spaced apart a distance of over two times the distance between adjacent microphones. The interpretations of the actors voice carry to the widely spaced-apart loudspeakers and provide the listener the opportunity to differentiate, unconsciously, the amplified components of the composite sound which, together with the actors direct voice, make up the total of the interpretation. My inven tion involves the novel positioning, spacing, and interconnection of the various microphones and loudspeakers employed in the communication channels.

The widely spaced loudspeakers are associated with adjacent curved sound reflecting surfaces which extend across the proscenium arch to provide a uniform distribution of the sound from the loudspeakers at each point within the theatre, or auditorium. The novel location of the sound distributors in the proscenium arch results in an arrangement wherein the distance from such loudspeakers to the listener is of the same order as the direct distance from the actor to the listeners whereby the direct sound from the actor reaches the listener prior to the amplified sound from the speaker without the need for time delay apparatus in the sound channels. As mentioned above, such precedence effect is desirable since the auditor intuitively assigns the direction of the sound source to the first sound component to reach him.

The loudspeaker arrangement at the proscenium arch comprises, preferably, two stereophonic sound distributing apparati of the type shown in my co-pending patent application Serial Number 720,114, filed March 1958, and entitled, Stereophonic Sound Distributor. Two such distributors are placed end-to-end across the stage so as to provide loudspeakers at the ends and center of the stage, such an arrangement being particularly useful in a three channel system which includes at least a pair of microphones connected to each loudspeaker with the microphones arranged in a repeating sequence across the stage. The loudspeakers which are associated with the curved sound reflecting surfaces of the's ystem are responsive to wide frequencies within the range of, say, 500* to 5000 cycles per second. For good quality sound, the lower and higher frequencies must also be included. Hence, with my novel arrangement, high and low frequency loudspeakers are located adjacent the mid-frequency loudspeakers in the proscenium arch for handling the respective high and low components of the sound, one set for each channel.

In theatres having a balcony, -a section'of the orchestra beneath the said balcony may be in the acoustic shadow of the loudspeakers located high in the proscenium arch. Subsidiary reinforcement of the sound thereunder is therefore necessary and is accomplished by means of loudspeakers located in the shadow and fed by one of the sound channels through a time delay device, the loudspeakers producing the mid-frequency range sounds. Amplified high frequency sounds are supplied to 'the area by tweeters located within the area, which tweeters, in accordance with my invention, operate with no delayed response.

Although any suitable time delay arrangement may be used, a 'novel arrangement comprising 'a pair of spaced acoustical lenses is preferred, one lens "acting as a projector, or loudspeaker, and the other as a pick-up, or microphone, the distance apart of such'lenses determining the time delay obtained thereby.

iAn object of this invention is the provision of a sound amplification system for use in theatres, and the like, which provides an illusion of wholly natural sound.

An object of this invention is theprovision of a sound distribution system which functions to "strengthen andreinforce'the soundfrom'the stage of a theatrein a manner whereby the-amplified sound appearst-o'come from the actors on the stage, and notfrorn loudspeakers employed in the system.

An object of this invention is the provision of an auditorium or theatre soundsystem which raises the level of the apparent voices from thestage to all parts of the auditorium.

-An object of this invention is the provision of -a sound system which adds clarity to the voices or sounds from the stage.

An" object of this invention is the provision of a system for accomplishing the above objects and advantages without danger of feedback in the amplification.

An object of this invention is the provision of a sound system which includes a plurality of sound channels each of :which is easily controlled by a'sound engineer during the stagingof a play,"or the like.

An object of this invention is the provision of a sound amplification system for use in an auditorium which system utilizes directional tweeter loudspeakers with no delayed response in conjunction with a lower frequency response loudspeaker system which has a delayed response.

These and other objects and advantages will become apparent from the following description when taken with the accompanying drawings. It will be understood that the drawings are for purposes of illustration and are to construed as defining the scope or limits of the invention, reference being had for the latter purpose to the appended claims.

In the drawings, wherein like reference characters denote like parts in the several views:

FIGURE 1 is a block diagram of a two-channel sound system in accordance with my invention including a diagrammatic plan view of a stage showing my novel microphonic distribution;

FIGURE 2 is similar to FIGURE 1 only showing a three-channel system employing three microphones in each channel;

FIGURE 3 is a plan view of a theatre showing a portion of my novel sound system;

FIGURE 4 is a longitudinal sectional view of the theatre shown in FIGURE 3, as well as illustrating features of FIGURE 2;

FIGURE 5 is a block diagram of the three-channel sound system employed in the auditorium; shown FIG- URES 3 and 4 and embodying my invention;

FIGURE 6 is a plan view of the proscenium loudspeaker arrangement of FIGURE 4 and embodying my invention;

FIGURE 7 is a front View of the proscenium loudspeaker arrangement;

FIGURE 8 is a diagrammatic view of a time delay arrangement which may be employed in the form of FIG- URE Sin accordance with'my invention; and

' FIGURE -9 is a modified form of the time delay shown in FIGURE 8 which may be similarly'employed and also embodying my invention.

Reference is first made to FIGURE 1 of the drawings whereinthere is shown a two-channel communication system embodying my invention and employed in a theatre which includes a stage 10 and auditorium 11. At least four footlight microphones, or pick-ups 12 are located at the stageapron, the microphones being positioned adjacent the 'footlights (not shown) across the stage in a manner well understood by those skilled in this art. The micro-phones are located with two microphones at each side of the longitudinal center of the stage and spaced equal distances apart, if desired. Thus, for example, if the stage is 30 feet across, the microphones may be spaced at approximately 6 .footintervalsl The output from the microphones feeds into individual preamplifiers 13 which are shown in block form and designatedPre- Amp in the drawings.

It will here be understood that in the two-channel communication system illustratedin FIGURE l, the individual channels are designated either right or left channels and, in the drawings and specification, the elements or components associated with the right channel have included in the identification thereof the letter R, while those in the left channel include the letter L in their designation. Thus, those microphones associated with the right channel are designated -12-R, while those associated with the left channel are designated ll-L. It will further here be noted that in accordance with normal theatre parlance, the orientation of the stage is determined as viewed by an individual standing on the stage and facing the auditorium whereby, as viewed in FIGURE 1, stage right is to the left of the longitudinal center of the stage while stage left is to the right thereof.

Continuing, now, the description of FIGURE 1, the outputs from the preamplifiers 13 are fed to amplifiers 14, with the outputs from the right'channcl preamplifiers 13-R being connected to the right channel amplifier 14-R and the outputs from the left channel preamplifiers being connected to the left channel amplifier 14-L. The output from the respective right and left channel amplifiers are individually connected to right and left channel loudspeakers, or transducers, 15R and 16-L directed to the listener in the auditorium 11. The term transducers, as later explained, includes recorder heads of recording apparatus. The speakers are preferably widely spaced apart, being located at opposite sides of the stage, for example, and each speaker 16 is preferably of the type having a directional response pattern such that the speaker output may be heard substantially throughout the theatre. Hence, it will be understood, that the loudspeaker system is preferably of the type such that with the same signal to each loudspeaker the intensity of the sound from the right loudspeaker 16-R is substantially equal to the intensity of the sound from the left loudspeaker lie-L in the auditorium.

With the novel location and arrangement of the microphones 12, as illustrated in the two-channel system of FIGURE 1, it will be understood that the actors, or speakers, voice substantially always reaches one microphone of each channel. That is, the actors voice generally reaches both a right channel microphone ll-R and a left channel microphone 12-L whereby an output is obtained from both channel loudspeakers 16-R and 16-L. Thus, if an actor is facing the auditorium from the position designated X in FIGURE 1, the two microphones at the right side of the stage will receive and carry his voice to both the right and left channel loudspeakers. The listener in the auditorium thereby receives the direct sound from the actor plus the sounds from the widely spaced apart loudspeakers 16, which sounds provide the two cars of every listener the opportunity to differentiate, unconsciously, the two amplified components and the direct component of the composite sound which make up the total interpretation. Intelligibility is markly increased by my arrangement wherein an actors voice reaches separate channel microphones and is carried independently to associated channel loudspeakers whereby a listener hears the actors voice directly as reinforced by outputs from at least two channel loudspeakers; the arrangement of the microphones being such that the actors voice substantially always reaches one microphone of each channel.

It will here be understood that although the sound emanates from widely spaced loudspeakers 16, the sound distributing system is not intended to create a stereophonic sound effect. As the speaking actor moves across the stage, his direct voice, of course, moves with him. -But as the actor moves from the position at the right side of the stage shown in FIGURE 1, to the left side, for example, his voice is first picked up by the microphones at the right side of the stage, then the two microphones adjacent the longitudinal center of the stage, and finally the two microphones at the left side of the stage. If a pronounced stereophonic effect were obtained, it would be apparent that the actor, in moving from the right ofthe stage to the left thereof, would appear to alternately move from right to left, then left to right, and then again from right to left. Such stereophonic effects are unnoticed by placing the microphones sufficiently close together where by the speakers voice is picked up simultaneously by microphones in both channels. An amplified stereophonic effect is unnecessary, anyway, since seeing the actor and hearing his direct voice is sufficient to locate him. However, a slight side preference is allowed for such that if for example the actor is on the extreme right he will only be picked up by the extreme right microphone 12-R and, therefore, the reinforcement will come only from the speaker 16-R.

It will here be further understood that the two-channel 6 wider stages, additional channel microphones, and associated preamplifiers may be employed, and the pattern, or sequence, of alternate left and right microphones extended, as necessary, or desired, to reach across the stage, with the outputs from alternate microphones being connected together andto one channel loudspeaker.

The sound distribution system of my invention is not limited to a two-channel system. Further improvements in intelligibility are obtained by the addition of channels to the system whereby additional components are directed to the listener in the auditorium. A practical sound system which includes three channels of communication and which embody my invention is shown in FIGURE 2 of the drawings. Referring, then, to FIGURE 2, it will be noted that in addition to right and left channels, the system includes a third, or center, channel, the elements and components of which center channel include the letter C in the designation thereof in the specification and drawings; 'It will be noted that microphones 12 are arranged in a manner wherein the sequence of microphones 12-R, 1241 and 12-L is repeated across the stage, the sequence repeating three times for a total of nine microphones in the illustrated arrangement. The microphones may be adjacent the stage floor level, as illustrated in FIGURE 4. Each microphone 12 feeds through an individual preamplifier 13, with the outputs from the right channel preamplifier 13-R being connected together and to the right channel amplifier 14-R the outputs from the center-channel preamplifiers 13C being-connected to the center channel amplifier 14-C and, likewise, the outputs from the left-channel preamplifiers 13-L being connected together and to the left channel amplifier 14-L. The right, center and left amplifiers 14-R, 14-0 and 14L feed right, center, and left loudspeakers, or transducers, 16-R, 16-C and 16L,'respectively, each of which loudspeakers preferably carries to all parts of the auditorium 11. (In FIGURE 2, two loudspeakers 16C are shown.) The loudspeakers may be mounted in the proscenium arch, as illustrated in FIGURE 4.

With the abovedescribed three-channel system, shown in FIGURE 2, the actors voice substantially always reaches three separate, but rather closely, spaced microphones from wherever he stands on stage, with each microphone carrying independently to the three channel loudspeakers 16-R, 16C and 16-L. Thu-s, if the actor is in the position identified X in FIGURE 2, he will see facing him three microphones for the three channels, and his voice is carried to the loudspeakers 16 which are widely spaced apart and located, preferably, in the proscenium arch. Thus, three interpretations of what the actor is saying carry to the spread out reproducers and give the two cars of every listener in the auditorium the opportunity to differentiate, unconsciously, the three components of the composite sound which, together with his direct voice, make up the total interpretation.- In all of the embodiments of the system of my invention, it is desirable that the loudspeakers of the different channels be widely spaced apart so that the amplified components received by the listener appear to originate at spaced distances. If the different channel loudspeakers are too close together, they provide, in effect, a point source for the amplified sound components. I have found, that, it is desirable that the distance between adjacent loudspeak ers of different channels be at least twice the distance between adjacent micro-phones, for good sound quality from the system.

The number of microphones employed in each channel will depend upon the width and depth of the stage. Thus, for a very narrow stage, relatively few microphones are necessary, whereas a wider stage requires additional microphones. I have found that a spacing of from about 5 to 7 feet for the microphones is suitable for most stages, although spacings of less than three feet have been found to be satisfactory. Such spacing is not critical and in the practical application is individually determined for each theatre. Further, a large number of adaptations and variations in the sequence of microphones across the stageare possible Within the scope of my invention. Thus, the three-channel "system is not limited to the arrangement of FIGURE 2 wherein nine microphones 12 are employed. If seven microphones are employed, for example, the microphone sequence across the stage can be right, center, left, center, right, center, left. An obvious arrangement for six microphones would be the sequence of right, center, left, right, center, left, and for five microphones the sequence could be left, right, center, left, right. Thus, it is apparent that each channel of communication does not necessarily employ identical numbers of channel microphones. All that is required is that the actors voice carry to two and preferably three mircophones of different channels, and thence to individual channel loudspeakers which are preferably widely spaced apart whereby the listener, at all times, receives two or three interpretations of what is said, which are amplified, plus the direct voice component. stood that in accordance with my invention, it is not sufficient, for example, that a number of spaced loudspeakers be fed by a single microphone. The system must include individual channel microphones independently feeding separate channel loudspeakers whereby a plurality of interpretations of the speakers'voice are carried to the listeners to give the two ears of every listener the opportunity to differentiate dimensionally such individual components of the sound as come to him independently in exactly the same manner as is normal sound. The use of more than three independent channels, while helpful, is not proportionately advantageous.

The systems shown in FIGURES 1 and 2, and described above, involve, at least, the mid-frequency audio range'of, say, 500* to 5000 cycles per second, which range is most important for giving general support, or reinforcement, to the actors voices for improved intelligibility thereof. However, for good quality sound, and further improvement of the intelligibility, it is necessary to add the lower frequencies in the range of about 50 to 500 cycles per second. Suitable low frequency loudspeakers, or woofers, may be included in the system to handle the low frequency sounds. Likewise, tweeters, or high frequency. loudspeakers should be included to carry the high frequencies response up to, say, 15,000 cycles per second from 5000 cycles per second; the high frequencies being most'necessary for transmission of sibilant speech sounds, which further promote clarity. It will here be understood, that in'the drawings Lois utilized to designate low range loudspeakers, or woofers, Hi designates a high range loudspeaker or tweeters, and M designates mid-range loudspeakers.

'It will be appaent that different theatres and halls having different acoustical properties may require different sound systems in order to properly cover every part of the audience area of such theatre, 'or hall. That is, a person in the second balcony of a theatre should be able to hear as clearly and audibly'as a listener in the orchestra. In FIGURES 3-5 of the drawings, there are shown sche- 'matic and diagrammatic presentations of a typical theatre having a three-channel sound system in accordance with my invention. Reference is first made to FIGURES 3 and 4, wherein plan and longitudinal cross-sectional views, respectively, of a theatre in purely diagrammatic form are shown, which theatre includes in addition to the stage an auditorium 11 which includes an orchestra pit 21, orchestra section '22, and first and second balconies 23 and 24, respectively. As seen in FIGURE 3, the sound system includes seven (7) microphones, located at the stage floor level (see FIGURE 4), and arranged in a sequence of Left, Center, Right, Center, Left, Center, Right across the stage apron. With the microphones at stage floor level, the source of sound from the actors mouth is generally sufficiently far from the microphones such that only a relatively-small overall intensity change is It will here be underg produced as a result of the actors movement nearer to, or further from, the microphones. A long rectangular enclosure 26, shown in cross-section in FIGURE 4, is located directly under the proscenium arch 27 in front of the curtain 28, and houses loudspeakers employed in the sound system of my invention. The sound distributor housed in the enclosure 26 is shown in greater detail in FIGURES 5 and 6 of the drawings; it being here noted that such distributor comprises, essentially, two stereophonic sound distributors placed end-to-end, with each stereophonic distributor being built in accordance with my above-mentioned copending patent application Serial Number 720,114. By locating the loudspeakers .high above the stage in the proscenium arch, it will be seen, from FIGURE 4, that the distance from such loudspeakers to listeners in the auditorium is of the same order as the direct distance from the actors on stage to the same said listeners. For this reason, no time delay device is needed in the communication channels feeding such loudspeakers in the proscenium arch to establish a condition wherein the actors voice reaches the listener directly prior to the amplified sound.

Reference is now made to FIGURE 5 which includes a block diagram of the speaker system for the theatre shown in FIGURES 3 and 4 above; FIGURE 5 including also a partial diagrammatic plan view of the theatre and illustrating the microphone and loudspeaker distribution therein. A center-channel microphone 12-C is located at the longitudinal center of the stage, and a series of Right, Center, Left, microphones is located at both right and left sides thereof. Again, all of the microphones are preferably substantially equally spaced apart. The microphone outputs are connected to individual preamplifiers 13 in the usual manner. Three channel amplifiers 14-R, 14-C and 14-L are included and are pro- 'vided with inputs from the associated Right, Center, and Left preamplifiers, respectively, whereby the right and left channel amplifiers each have inputs from two preamplifiers while three preamplifiers 13-C supply inputs to the center channel amplifier.

As mentioned above, maximum intelligibility and clarity with the sound system is obtained when the system responds to substantially the entire audio frequency range of signals of from, say, 4,045,000 cycles per second. In a practical system, such as illustrated in the FIGURE 5, the wide range of frequency reproduction is provided by the use of woofer, mid-range and tweeter loudspeakers. As seen in FIGURE 5, the output from each channel amplifier 14 is carried to individual threeway filters, or crossovers 31 for distribution of the channel amplifier outputs to appropriate loudspeakers; the '40-50 00 cycle per second range being fed to the midrange loudspeakers 16, and the SGM -15,000 cycle per second range being fed to tweeters 33, all of which loudspeakers 16, 32 and 33 are located in the enclosure 26 (FIGURE 4) in the proscenium arch 27. If necessary, in large theatres, the mid-range frequencies from the crossover 31 may be fed to two mid-frequency range loudspeakers 16 in each channel of the system, as illustrated in' FIGURE 5, for sufiicient output to fill the theatre.

It will here be understood that the preamplifiers 13 and channel amplifiers 14 are provided with individual gain controls whereby the amplification level of each is controllable. The preamplifiers 13 are adjusted to provide substantially equal amplitude outputs for equal inputs to the microphones 12. During a stage production, the sound engineer only changes the gain of the channel amplifiers 14 for control of the general level of the total response, increasing the gain for the weaker voices, as desired.

The sound amplification, or reinforcement, system, described thus far, is adequate for substantially all areas of the auditorium where there is a straight, unobstructed, line from the loudspeakers in the proscenium arch to s the listener. As a result, substantially the entire second and first balconies 24 and 23 (FIGURE 4) are well covered, as well as the front section of the orchestra seats. It may be advisable, however, to increase the very high frequency coverage in the second balcony because of the long distances the sound must travel from the proscenium arch loudspeakers thereto; the level of the high frequency sounds diminishing rapidly with distance. The high frequency range sounds in the second balcony may be further reinforced by use of high frequency transducers, or tweeters, 36-R and 36L connected through lines 37 to the right and left channel amplifiers 31R and 31-L, respectively, as seen in FIGURE 5. As shown in FIG- URES 3 and 4, such loudspeakers 36 may be mounted on each side of the second balcony adjacent the point that the balustrade 38 meets the theatre side walls, with the axes defined by perpendiculars extending from the centers of the radiations of the loudspeakers extending diagonally back to the opposite rear corners of the auditorium whereby the sound from the right loudspeakers 36R covers, particularly, the left side of the second balcony, and the sound from the left loudspeaker 36-L covers the right side thereof. With this arrangement, the distance from the tweeters 36 to the listener in the second balcony is of the same order as the distance of the actors to the said listener, whereby no time delay mechanism is necessary to maintain the emphasis on the direct sound from the stage.

As best seen in FIGURE 4, the front of the orchestra section 22 is well covered by the proscenium loudspeakers. The rear-most section of the orchestra under the first balcony is, however, within an acoustical shadow created by that portion of the first balcony which intersects the straight line path between the proscenium loudspeakers and a portion of the orchestra section. This is not true, however, for low frequencies from the proscenium Woofers 32, since the low frequency sound therefrom bends enough to cover the entire orchestra area well. For higher frequencies, however, it is necessary to provide additional loudspeakers to reinforce the sound in this area. Ordinarily, theatres are provided with light canopies in this area, which provide ideal locations for additional loudspeakers. One suitable arrangement comprises locating a cluster 41 of sixteen loudspeakers 42 at each of three light canopies located above the back orchestra seats. Each cluster is arranged in banks of four loudspeakers, with the banks forming a square. Further, the loudspeakers face upwardly at an angle of, say, 45 dedegrees whereby the sound therefrom is reflected off the ceiling before reaching the listener. All of the loudspeakers 42 are energized by an output from the center channel amplifier 14-C connected thereto through a delay line 44, forms of which are illustrated in detail in FIG- URES 8 and 9. In order to avoid expense, only one delay line need be used in the system. (Obviously, each cluster of loudspeakers could be driven by outputs from the individual channel amplifiers 14, through three separate delay lines, if desired.) The delay line may comprise, for example, a long coiled copper tube having a small loudspeaker transducer at one end thereof energized by the output from the central channel amplifier 14-L. A pick-up unit at the other end of the tube, which is similar to the loudspeaker may be used to pick-up the energy after it has travelled the length of the tube in a little less than one-twentieth of a second. An amplifier 45 can be used to amplify the sound from the tube to drive the total of forty eight small speakers 42. The frequency response of such a delay line is inversely pro portional to the frequency such that it is necessary to equalize the response materially. Further, there is an upper limit of about 5,000 cycles per second which cannot be economically exceeded. The loudspeakers 42 are, therefore, limited to the mid-frequency range of about 5004000 cycles per second.

sesame For the high frequency response in the area under the first balcony, a pair of tweeters 47 are employed at each cluster 41. As seen in FIGURE 5, one tweeter of each pair thereof is pointed rearwardly to the right and the other is pointed rearwardly to the left. The one pair of tweeters 47-R and 47-C at the right side of the auditorium are energized by outputs from the right and center channel amplifiers 14-R and 14C, respectively, the pair of tweeters 47-L and 47-R at the center canopy being energized by outputs from the left and right channel amplifiers i i-L and 14R, respectively, and the pair of tweeters 47-C and 47-L at the left side of the auditorium being energized by the outputs from the center and left channel amplifiers, respectively. I have discovered that the tweeters 47 may be energized without the use of a time delay. Thus, in accordance with my invention directional tweeter loudspeakers, with no delay response, are used with a lower frequency response loudspeaker system which has a delayed response. The level of the output of the tweeters 47 is adjusted to be low enough never to call attention to them. The delayed center channel energy to the mid-range loudspeakers 42 in the canopies covers the basic sensory frequency band sufficiently such that the actor-to-listener precedence is maintained, with the undelayed tweeters 47 merely filling in with the needed sibilents. The output level adjustments for the loudspeakers 41 and 47 must be carefully made with respect to each other, but once made, no further adjustment is necessary. Of course, when the sound engineer adjusts the level of the channel amplifier 14 outputs, the input to all the loudspeakers connected to such amplifiers varies simultaneously for each ch-an nel, so that the ratio of the levels remain constant.

An objectional feature of sound systems which cannot be tolerated, yet, which is most difficult to overcome is feedback; feedback occurring when the sound from the loudspeakers impinges on the rnicrophonhes at a sufficiently high level so that the feedback loop oscillates producing a ringing quality to the sound or a continuing singing tone. In prior art arrangements, wherein a plurality of pickups, or microphones are employed, it is often necessary for the sound engineer, or operator, to switch off those microphones not being used, or substantially lower the gain of the amplifiers connected thereto. With the novel microphone and loudspeaker distribution of my invention, the microphones may be kept open at all times and adequate amplifier gain maintained, without feedback effects. This may be demonstrated by turning the gain of the channel amplifiers 14-R and 14L down and adjusting the gain of the center channel amplifier l kC up to the feedback point and then dropping the gain thereof back slightly from feedback for safety. The position of the gain control is noted and the left channel amplifier gain is brought up and backed off in the same manner and its position noted. The same is done for the right channel amplifier. Then, all of the amplifier gains are brought up to their respective safe positions and it will be noted that there is no increase in the tendency to feedback. The actual output is three fold stronger, as well as much clearer, whereby the gain of each may be turned down further some three db so that there is no possible chance of feedback. Furthermore, the sound does not have any ringing quality which comes when the feedback position is even safely approached. The operator, or sound engineer, is able, therefore, to adjust the amplifier gain within a wide range without chance of feedback. Further, the diminution in the tendency to feedback applies in the situation wherein the microphones 12 are quite close together, with a spacing of only several feet therebetween.

Reference is now made to FIGURES 6 and 7 of the drawings wherein front and plan views, respectively, in diagrammatic form, of the loudspeaker arrangement in the proscenium arch of FIGURE 4 are shown. As mentioned above, such arrangement comprises, essentially,

s eared two stereophonic sound distribution systems of the type shown in my above-mentioned copending patent application Serial Number 720,114, arranged in an end-to-end placement. The mid-range loudspeakers 16 are associated with reflecting members 51 each having a convexly curved reflecting surface. Such loudspeakers 16 are mounted adjacent the reflecting surfaces and arranged in a manner whereby the axes defined by perpendiculars extending from the centers of the radiators of the loudspeakers extend generally tangentially to the said associated reflecting surface, with the axes of the center channel loudspeakers extending divergently, while those of the right and left channel loudspeakers extend convergently. By using loudspeakers 16 having a directional response pattern which includes an elongated major lobe, and mounting them, as illustrated, the sound from each of the loudspeakers and associated generally co-nvexly curved reflecting surface covers substantially the entire auditorium of the theatre, a response pattern for the loudspeakers 16-R and associated reflecting surface 51 being indicated by a broken line designated 53 in FIGURE 3. It will be noted in FIGURES 6 and 7 that of the two mid-frequency range loudspeakers 16-C in the center of the distributor, the axis from the radiator of one loudspeaker extends to the right while the axis of the other extends to the left adjacent the associated reflecting surfaces whereby the combination of two center channel mid-frequency range loudspeakers covers substantially the entire auditorium (except for acoustical shadows, as mentioned above, created by overhanging balconies, and the like). An important feature of the arrangement of the loudspeakers 16 and reflecting surfaces 61 resides in the fact that with the illustrated arrangement the intensity of the sound from one pair of channel loudspeakers 16 is substantially equal to the intensity of the sound from each of the other pair of loudspeakers anywhere in the theatre auditorium in direct view of the loudspeakers.

As mentioned above, time delay mechanisms which utilize magnetic recording and playback equipment are not very satisfactory since rotating equipment is necessary whereby continuing maintenance is required, and most contemporary static delay lines are either rather expensive or have many shortcomings which include poor frequency response. Reference is made to FIGURE 8 of the drawings wherein there is shown a static delay line in accordance with my invention, which is inexpensive and which responds well up into the high frequency range. The delay mechanism includes a pair of transducers 56 having conical horns 57. The front of the horns are provided with acoustic lenses 58. Acoustic lenses are Well known in the art and may comprise, for example, a plurality of shaped louvers which are wider in the center than at the edges whereby the sound therethrough is delayed more at the circular center front than at the edges. The horns which are directed toward each other may be coaxially positioned at any desired separation, depending upon the delay desired. One transducer is utilized as a loudspeaker, while the other functions as a pick-up. With an input signal to the loudspeaker, a sheaf of parallel sound rays is directed therefrom to the other horn, and associated pick-up, the time required for the sound to travel from the loudspeaker to the pick-up depending upon the spacing designated X, between such transducers. Thus, a wide range of time delays is possible by adjustment of the spacing between horns. Unlike many prior art arrangements, the system responds well to signals within the range of about 1000 to 15,000 cycles per second.

The overall length between transducers of the time delay mechanism of FIGURE 8 can be reduced by the arrangement of FIGURE 9, for equal time delays. Referring, then, to FIGURE 9, it will be seen that the system may include a reflecting member 61 having a sound reflecting surface 62. The horns are arranged such that the axes X/2 defined by perpendiculars extending from the transducers intersect at a point on the reflecting surface 62 at equal angles wtih the reflecting surface. The orientation is such that the reflected sound from one transducer, functioning as a loudspeaker, is directed to the other transducer. The distances from the transducers to the reflecting surface are equal to X/ 2 for the same time delay provided by the arrangement of FIGURE 8. For a thirty millisecond time delay, the acoustical distance X between the transducers must be about thirty feet. The time delay mechanism of either FIGURE 8 or 9 may generally easily be installed in the space existing between floors or balconies in most theatres. The illustrated time delay mechanism may be utilized as the time delay 44 shown in block diagram form in FIGURE 5.

Having now described my invention in detail, in accordance with the requirements of the patent statutes, various changes and modifications will suggest themselves to those skilled in this art. For example, in the three communication channel system which includes right, left and center microphones, the center loudspeaker, or loudspeakers, may be eliminated from the system and the output from the center microphone fed to the right and left loudspeaker, or loudspeakers, with equal amplitude. An arrangement wherein the output from a center microphone is fed equally to left and right loudspeakers, which loudspeakers are fed also by individual left and right microphones, is known as a phantom arrangement, and it is herein pointed out that the phantom arrangement is applicable to the novel arrangement of my invention. Furthermore, it will be understood that my invention is applicable in arrangements wherein a recording link is interposed in the system between the microphones and loudspeakers. For example, the output from the right and left amplifiers in the two channel system (of the type shown in FIGURE 1, e.g.) may be fed to recorder heads, or transducers, and the output recorded on individual channels of a two channel recording medium, such as a magnetic tape or recording disc. During playback, the output from the playback heads would be fed to individual loudspeakers, as described above. For a three channel system (of the type shown in FIGURE 2 e.g.) the outputs from the individual left, right and center amplifiers, for example, may be recorded on individual channels of a three-channel recording medium. Three separate pickups may be employed to obtain from the recording medium three individual outputs for application to individual right, left and center loudspeakers; or in the case of a phantom arrangement, the output from the center channel may be fed equally to the right and left loudspeakers. Recording apparatus for use in such system is well known in the art. It is intended that the above, and other such changes and modifications shall fall within the spirit and scope of the invention, as recited in the following claims.

I claim:

A sound distribution system for a theatre, or the like, comprising, a plurality of spaced right channel microphones and left channel microphones arranged in a line across the stage with at least one right channel microphone and one left channel microphone at each side of the longitudinal center of the stage; a center channel microphone positioned adjacent the longitudinal center of the stage between a right and left channel microphone; right and left channel loudspeakers; a center channel loudspeaker; means connecting the right channel microphones to the right channel loudspeakers and means connecting the left channel microphones to the left channel loudspeakers, sound from both left and right channel loudspeakers normally being audible within an area of the theatre; and means connecting the center channel microphone to the center channel loudspeaker, sound from the center channel loudspeaker normally being audible within the said area wherein sounds from the right and left channel loudspeakers are also audible.

(References on following page) 13 14 References Cited in the file of this patent 2,846,504 Mikulyak Aug. 2, 1952 UNITED STATES PATENTS 2,846,514 y 1 195 2,137,032 Snow Nov, 15, 1938 FOREIGN PATENTS 2,298,618 Garity Oct 1 4 5 1,002,395 Germany 14, 1957 2,481,911 De Boer et a1 Sept. 13, 1949 OTHER REFERENCES 2,783,677 Becker Mar. 5, 1957 Feldman: The Case for a Third Channel, Radio and 218191342 Becker 1958 92 News March 1959, pgs. 7071 and 104-105. 

